Marking twist-drills



(No Model.)

G. L. HOLT. MARKING TWIST DRILLS.

No. 460,639. Patented Oct. 6, 1891.

fiiE mama mien: co., momumq, wumucnuu, u. c.

UNITED STATES PATENT OFFIC GARDNER L. HOLT, OF SPRINGFIELD, MASSACHUSETTS.

MARKING TWIST-DRILLS.

SPECIFICATION forming part of Letters Patent No. 460,639, dated October 6,1891.

Application filed March '7, 1889. Serial No. 302,004. (No model.)

To a whom, it nuty concern:

Be it known that I, GARDNER L. HOLT, of Springfield, in the county of Hampden and State of Massachusetts, have invented a certain new and useful Improvement in Marking. Drills and Bits, whereof the following is a specification, reference being had to the accompanying drawing, in which the figure represents in elevationadrill having the number indicating its size marked in its groove in my improved method.

My invention consists in stamping orotherwise marking the number or other mark or marks indicating the size of a twist drill or bit in the groove of the same.

\Vhen'drills are marked in the usual way, which is on the periphery, where they are gripped by the chuck or by the jaws of a bitbrace, or where the surface is worn by the friction of the material around the hole being bored, the marking is very soon obliterated or rendered indistinct by the mutilation of the drill by the chuck or brace or the wearing of the same in the material drilled. A constant inconvenience is thereby caused the workmen using such tools, who are compelled often to select them by the use of calipers,

and mistakes of size often occur, causing damage to the work. These evils are obviated by placing the marking in the groove, because it is there protected from the grip and wear of use by the depression wherein it is. The mark is also more conspicuous when the drill is put away in the usual rack.

The marking may be made in the usual way by a hand or power press supporting the drill or bit by a die underneath it conforming to its configuration, and impressing the marking, out in the usual manner upon an upper die, or by any of the usual modes. In smaller grooves the marking may be made longitudinally in the groove in an elongated form, (thus 3-8 instead of to permit the use of larger figures, if desired.

What I claim as my invention, and for which I pray Letters Patent, is

A twist-drill having the markingindioating its size made in its groove, substantially as described.

GARDNER L. HOLT.

In presence of JosEPH R. CHURCH,

NELSON W. MERRILL. 

